Arbitrary Waveform and Function Generator (AFG) instruments are widely utilized for generating continuous/burst user-defined mathematical function waveform signals for electronic circuit design and testing. Typically, an AFG instrument has an output impedance of 50 ohms over its operating frequency range. The load impedance of a device under test (DUT) impacts the actual output signal of an AFG instrument.
During a typical operation, a low insertion-loss cable is generally used to connect the AFG to a DUT. For low frequencies and matching loads, the waveform monitoring function of the AFG works well with a minor cable attenuation that is easy to compensate. However, at high frequencies, i.e., when the cable length is comparable to the signal wave length and the load impedance of a DUT is mismatched with the AFG output impedance, the measurement results in the local output point of the AFG might be quite different than the actual signals loaded to the remote point of the DUT, due to the impedance transformation of the transmission line, which will be called the cable effect hereinafter.